If the control voltage available exceeds the input requirements for a Power-io product, you have two choices.
You can use a zener diode to change the control input voltage. For example: a typical Power-io control input is 4-32 VDC = ON and <1 volt = OFF. If you insert a zener diode, you can offset those ranges by the value of the zener diode.
For example: if you have a 48 VDC control signal, then insert a 20 volt zener diode. The Power-io control input range changes from 4-32 VDC to 24-52 VDC = ON and <21 VDC = OFF.
OR you can use a voltage divider to reduce that voltage to an acceptable amount. For example: if you have a 48 VDC control signal and you wish to use a Power-io product that has a input requirement of 4-32 VDC and 0.010 amps (10 mA). You decide that you would like to have a 12 VDC signal for this Power-io application. Enter the first 3 items below, click calculate, and you see that you should use a 3600 ohm and 1200 ohm resistor.
OR, click reset, insert the starting voltage, amperage requirement, and the values of 2 resistors that you might already have available. Click calculate to see if they generate a control signal that is with-in the requirements of the Power-io product.
The control input requirements for most Power-io products is fairly broad so many easy-to-obtain resistor combinations will provide an acceptable solution.